some of my shallots have gone soft

Question

I have planted them in 10 litre pots. They are outside since middle of February. what can be the problem.

Answer 1

Have you had cold weather?
It sounds to me cold damage, that they may have been exposed to a freeze.
Over watering without proper drainage would also be a concern.

Here is a link about the proper care of shallots.

https://www.gardeningknowhow.com/edible/vegetables/shallot/planting-shallot-sets.htm